Evaluating Degradation Mechanisms in Post-Consumer Polyolefin Flake
Polyolefin degradation evaluation requires coupling multi-load melt flow testing and OIT analysis to quantify chain scission and restabilize flake lots.
Carbonyl Index FTIR
Meaning
An analytical metric quantifies the extent of oxidation in a polymer by measuring the ratio of carbonyl absorbance to a reference polymer band using infrared spectroscopy. This measurement, known as carbonyl index ftir, allows laboratory technicians to track the chemical aging of moulded parts and raw materials. The resulting values correlate directly with the reduction in mechanical performance of the polymer.
Analytical Method
Infrared spectroscopy sweeps through the infrared spectrum to record the absorption peaks of the oxidized polymer matrix. Oxidation generates carbonyl compounds like ketones, aldehydes, and carboxylic acids, which produce a distinct peak. Dividing the height of this carbonyl peak by the height of an unchanged reference peak, such as the methylene bending peak, yields a normalized value.
This normalization removes the effect of sample thickness and variation in surface contact.
Quality Control
Moulders utilize this spectroscopic technique to audit incoming shipments of recycled resin for degradation. High baseline index values indicate that the plastic has already suffered thermal or environmental damage. Such materials are likely to produce brittle moulded components that fail under impact tests.
Recycled Content
Sourcing post-consumer resins requires strict threshold limits on the carbonyl level of the raw flake. Although a material datasheet might show acceptable melt flow rates, a high spectroscopic index reveals latent degradation that will appear as mechanical failure during long-term part service.